Detecting method and device for capacitive touch screen

ABSTRACT

A detecting device and method for a capacitive touch screen is proposed. The present invention employs a multiple-electrode driving mode, which sequentially drives sets of driving electrodes among driving electrodes. A reduced image is generated from the signals of a plurality of detecting electrodes. In addition, a single-electrode driving mode is employed to drive the first and the last driving electrodes, respectively, thereby obtaining first- and second-side 1D sensing information for single-electrode driving from the signals of the detecting electrodes, respectively. An expanded image can be generated based on the first-side 1D sensing information for single-electrode driving, the reduced image and the second-side 1D sensing information for single-electrode driving in order to detect approaches or touches made by external conductive objects to the capacitive touch screen.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/648, 710, filed on May 18, 2012, which are herein incorporated byreference for all intents and purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to detecting method and device forcapacitive touch screens, and more particularly, to device and methodfor generating an image by single-electrode driving andmultiple-electrode driving.

2. Description of the Prior Art

A capacitive touch screen determines the locations of touches made by ahuman body thereon based on changes in detected signals due to itscapacitive coupling with the body. When the human touches the screen,noise surrounding the human body also adds to the capacitive couplingbetween the human body and the capacitive touch screen, and thus causingchanges in the detected signals. Moreover, since noise is not constant,it cannot be easily determined. When the signal to noise ratio (S/Nratio) is relatively small, a touch may not be detected, or the locationof the touch may not be accurately detected.

From the above it is clear that prior art still has shortcomings. Inorder to solve these problems, efforts have long been made in vain,while ordinary products and methods offering no appropriate structuresand methods. Thus, there is a need in the industry for a novel techniquethat solves these problems.

SUMMARY OF THE INVENTION

An objective of the present invention is to address the inappropriateS/N ratio of the capacitive touch screen caused by noise coming from ahuman body. The present invention therefore proposes a detecting deviceand method for a capacitive touch screen. The present invention employsa multiple-electrode driving mode, which sequentially drives sets ofdriving electrodes among driving electrodes. A reduced image isgenerated from the signals of a plurality of detecting electrodes. Inaddition, a single-electrode driving mode is employed to drive the firstand the last driving electrodes, respectively, thereby obtaining first-and second-side 1D sensing information for single-electrode driving fromthe signals of the detecting electrodes, respectively. An expanded imagecan be generated based on the first-side 1D sensing information forsingle-electrode driving, the reduced image and the second-side 1Dsensing information for single-electrode driving in order to detectapproaches or touches made by external conductive objects to thecapacitive touch screen. Multiple-electrode driving produces signalswith a better S/N ratio compared to the single-electrode driving. Thepresent invention provides improved S/N ratio while maintaining acoordinate detecting range (resolution) the same as that of a full imagegenerated in the single-electrode driving.

Said and other objectives of the present invention and the solutions forthe prior-art problems are achieved by the following technical schemes.A detecting device for a capacitive touch screen proposed by the presentinvention includes: a capacitive touch screen including a plurality ofdriving electrodes and a plurality of detecting electrodes, wherein thedriving electrodes and the detecting electrodes cross each other at aplurality of intersections; a driving circuit for providing a drivingsignal, wherein in a single-electrode driving mode, the driving signalis provided to only one of the driving electrodes at a time, while in amultiple-electrode driving mode, the driving signal is simultaneouslyprovided to a set of driving electrodes at a time, wherein apart fromthe last N driving electrodes, each driving electrode and two successivedriving electrode construct the set of driving electrodes beingsimultaneously driven, and N is the number of the set of drivingelectrode minus one; and a detecting circuit, each time the drivingsignal being provided, obtaining one-dimensional (1D) sensinginformation from the detecting electrodes, wherein in themultiple-electrode driving mode, a 1D sensing information formultiple-electrode driving is obtained when each set of drivingelectrodes are provided with the driving signal, and in thesingle-electrode driving mode, a first-side 1D sensing information forsingle-electrode driving and a second-side 1D sensing information forsingle-electrode driving are obtained when the first driving electrodeand the last driving electrode are provided with the driving signal,respectively; and a control circuit for generating an image based on thefirst-side 1D sensing information for single-electrode driving, all the1D sensing information for multiple-electrode driving and thesecond-side 1D sensing information for single-electrode driving.

Said and other objectives of the present invention and the solutions forthe prior-art problems are also achieved by the following technicalschemes. A detecting method for a capacitive touch screen proposed bythe present invention includes: providing a capacitive touch screenincluding a plurality of driving electrodes and a plurality of detectingelectrodes, wherein the driving electrodes and the detecting electrodescross each other at a plurality of intersections; providing a drivingsignal, wherein in a single-electrode driving mode, the driving signalis provided to only one of the driving electrodes at a time, while in amultiple-electrode driving mode, the driving signal is simultaneouslyprovided to a set of driving electrodes at a time, wherein apart fromthe last N driving electrodes, each driving electrode and two successivedriving electrode construct the set of driving electrodes beingsimultaneously driven, and N is the number of the set of drivingelectrode minus one; and each time the driving signal being provided,obtaining one-dimensional (1D) sensing information from the detectingelectrodes, wherein in the multiple-electrode driving mode, a 1D sensinginformation for multiple-electrode driving is obtained when each set ofdriving electrodes are provided with the driving signal, and in thesingle-electrode driving mode, a first-side 1D sensing information forsingle-electrode driving and a second-side 1D sensing information forsingle-electrode driving are obtained when the first driving electrodeand the last driving electrode are provided with the driving signal,respectively; and generating an image based on the first-side 1D sensinginformation for single-electrode driving, all the 1D sensing informationfor multiple-electrode driving and the second-side 1D sensinginformation for single-electrode driving.

With the above technical schemes, the present invention at least has thefollowing advantages and beneficial effects:

1. The S/N ratio is raised by the simultaneous multiple-electrodedriving frequency; and

2. The detection range the same as that of the full image is obtained bythe expanded image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 and FIG. 4 are schematic diagrams illustrating capacitive touchscreens and control circuits thereof according to the present invention;

FIG. 2A is a schematic diagram illustrating a single-electrode drivingmode;

FIGS. 2B and 2C are schematic diagrams illustrating a two-electrodedriving mode;

FIGS. 3A and 3B is a flowchart illustrating a detection method for thecapacitive touch screen according to the present invention;

FIG. 5 is a schematic diagram illustrating the generation of a fullimage;

FIG. 6 is a schematic diagram illustrating the generation of a reducedimage;

FIGS. 7A and 7B are schematic diagrams illustrating the generation of anexpanded image; and

FIG. 8 is a flowchart illustrating the generation of the expanded imageaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of the present invention are described in detailsbelow. However, in addition to the descriptions given below, the presentinvention can be applicable to other embodiments, and the scope of thepresent invention is not limited by such, rather by the scope of theclaims. Moreover, for better understanding and clarity of thedescription, some components in the drawings may not necessary be drawnto scale, in which some may be exaggerated relative to others, andirrelevant parts are omitted.

Capacitive touch screens are vulnerable to noise, especially, thatcoming from the human body touching the screen. The present inventionachieves the objective of reducing noise interference with an adaptivedriving scheme.

In a capacitive touch screen, a plurality of electrodes arranged in rowsand columns are used for detecting locations of the touches, in whichpower consumption is proportional to the number of simultaneously drivenelectrodes and the driving voltage. During touch detecting, noise maytravel to the capacitive touch screen via the conductor touching thescreen, degrading the signal to noise ratio (S/N ratio) and causingmisjudgment of a touch or the location of a touch. In other words, theS/N ratio dynamically changes according to the object touching thescreen as well as the surrounding environment.

Referring to FIG. 1, a schematic diagram illustrating a capacitive touchscreen and a control circuit thereof according to the present inventionis shown. It includes a clock circuit 11, a pulse width modulation (PWM)circuit 12, a driving switch 131, a detecting switch 132, a drivingselecting circuit 141, a detecting selecting circuit 142, at least onedriving electrode 151, at least one detecting electrode 152, a variableresistor 16, an amplifying circuit 17 and a measuring circuit 18. Thecapacitive touch screen may include the plurality of driving electrodes151 and the plurality of detecting electrodes 152 crossing each other toform a plurality of intersections.

The clock circuit 11 provides a clock signal for the entire system basedon a working frequency, and the PWM circuit 12 provides a PWM signalbased on the clock signal and a PWM parameter to drive the drivingelectrodes 151. The driving switch 131 control the driving of thedriving electrodes, and the selecting circuit 141 selects at least onedriving electrode 151. In addition, the detecting switch 132 controlsthe electrical coupling between the driving electrodes and the measuringcircuit 18. When the driving switch 131 is turned on, the detectingswitch 132 is turned off, the PWM signal is provided via the drivingselecting circuit 141 to driving electrode(s) 151 coupled by the drivingselecting circuit 141, wherein there can be a plurality of drivingelectrodes 151, and the selected driving electrode(s) 151 can be one,two, or more. When a driving electrode 151 is driven by the PWM signal,capacitive coupling 152 will be generated at intersections of detectingelectrodes 152 and the driving electrode 151 being driven, and eachdetecting electrode 152 will generate an input signal when capacitivelycoupled to the driving electrode 151. The variable resistor 16 providesimpedance based on a resistor parameter, and the input signal isprovided to the detecting selecting circuit 142 via the variableresistor 16. The detecting selecting circuit 142 selects one, two,three, multiple or all of the detecting electrodes 152 to couple withthe amplifying circuit 17. The input signal is amplified by theamplifying circuit 17 based on a gain parameter and then provided to themeasuring circuit 18. The measuring circuit 18 detects the input signalbased on the PWM signal and the clock signal, wherein the measuringcircuit 18 samples the detected signal with at least one phase based ona phase parameter. The measuring circuit 18 can, for example, include atleast one integration circuit. Each integration circuit performsintegration on an input signal in the input signal with at least onephase based on the phase parameter to measure the magnitude of the inputsignal. In an example of the present invention, each integration circuitperforms integration on a pair of input signals in the input signal withat least one phase based on the phase parameter, or performs integrationon the difference between signal differences of two pairs of inputsignals in the input signal with at least one phase based on the phaseparameter. Moreover, the measuring circuit 18 may further include atleast one analog-to-digital converter (ADC) to convert the detectionresult into a digital signal. In addition, it can be appreciated by onewith ordinary skill in the art that the input signal can be firstamplified by the amplifying circuit 17 before providing to the measuringcircuit 18 by the detecting selecting circuit 142; the present inventionis not limited as such.

In the present invention, capacitive touch screens have at least twotypes of driving modes: a power saving single-electrode driving mode,and a two-electrode driving mode, and have at least one drivingpotential. Each driving mode corresponding to a different drivingpotential has at least one working frequency. Each working frequencycorresponds to a set of parameters. Each driving mode corresponding to adifferent driving potential represents power consumption of a differentlevel.

The electrodes of a capacitive touch screen are divided into a pluralityof driving electrodes and a plurality of detecting electrodes. Thedriving electrodes and the detecting electrodes cross each other atnumerous intersections. Referring to FIG. 2A, in the single-electrodedriving mode, driving electrodes are driven one at a time, that is, inany one instance, only a single driving electrode is provided with adriving signal S. When any driving electrode is driven, signals of allof the detecting electrodes are detected to generate one-dimensional(1D) sensing information. Accordingly, after all the driving electrodesare driven, 1D sensing information corresponding to every drivingelectrode is obtained, which together constitute a full imagecorresponding to all intersections.

Referring to FIGS. 2B and 2C, in the two-electrode driving mode, a pairof adjacent driving electrodes is driven at a time. In other words, ndriving electrodes require n−1 times of driving. When any pair ofdriving electrodes is driven, signals of all of the detecting electrodesare detected to generate 1D sensing information. For example, first, asshown in FIG. 2B, a driving signal S is simultaneously provided to afirst pair of driving electrodes. Then, as shown in FIG. 2C, the drivingsignal S is simultaneously provided to a second pair of drivingelectrodes, and so on. Accordingly, after every pair (total of n−1pairs) of driving electrodes are driven, 1D sensing informationcorresponding to every pair of driving electrodes is obtained, whichtogether constitute a reduced image in comparison to the full image. Thenumber of pixels of the reduced image is less than that of the pixels ofthe full image. In another example of the present invention, thetwo-electrode driving mode further includes perform single-electrodedriving on electrodes at either end. When the electrodes at either endare driven, signals of all the detecting electrodes are detected togenerate 1D sensing information, together they provide two 1D sensinginformation, which form an expanded image with the reduced image. Forexample, 1D sensing information corresponding to either side is placedoutside the two sides of the reduced image to form the expanded image.

It can be appreciated by one with ordinary skill in the art that thepresent invention may also include three-electrode driving mode,four-electrode driving mode and the like, and they will not be furtherillustrated to avoid redundancy.

The driving potential may include, but is not limited to, at least twodriving potentials, such as a low driving potential and a high drivingpotential. A higher driving potential has a higher S/N ratio.

According to the above, in the single-electrode driving mode, a fullimage can be obtained, whereas in the two-electrode driving mode, areduced image and an expanded image can be obtained. The full image, thereduced image and the expanded image can be obtained before or when anexternal conductive object 19 approaches or touches the capacitive touchscreen. The external conductive object 19 can be one or more. Asmentioned before, when the external conductive object 19 approaches ortouches the capacitive touch screen, or capacitive couples with thedriving electrode(s) 151 and the detecting electrode(s) 152, noiseinterference may arise, even when the driving electrode 151 is notdriven, the external conductive object 19 may still capacitive couplewith the driving electrode(s) 151 and the detecting electrode(s) 152.Moreover, noise may interfere through some other routes.

Accordingly, the present invention provides a noise detecting processfor detecting noise interference. During the noise detecting process,the driving switch 131 is turned off, and the detecting switch 132 isturned on, such that the measuring circuit can generate 1D sensinginformation of noise detection based on the signals of the detectingelectrodes 152, thereby determining if the noise interference is withina tolerable range. For example, whether the noise interference is withinthe tolerable range can be determined by determining whether the 1Dsensing information of noise detection exceeds a threshold, or whetherthe sum or the average of all the values of the 1D sensing informationof noise detection exceeds a threshold. It can be appreciated by onewith ordinary skill in the art that there are other ways of determiningwhether the noise interference is within the tolerable range based onthe 1D sensing information of noise detection, which the presentinvention will not further illustrate.

The noise detecting process can be performed when the system isactivated, or every time the full, the reduced, or the expanded image isobtained, or regularly or multiple times when the full, the reduced, orthe expanded image is obtained, or when an approaching or touch by anexternal conductive object is detected. It can be appreciated by onewith ordinary skill in the art that there are other suitable timings forperforming the noise detecting process; the present invention is notlimit to these.

The present invention further proposes a frequency switching process forswitching frequencies when the noise interference exceeds the tolerablerange. The measuring circuit is provided with several sets of frequencysettings, which can be stored in a memory or other storage media and canbe selected by the measuring circuit during the frequency switchingprocess. The clock signal of the clock circuit 11 is thus controlled bythe selected frequency. The frequency switching process may includeselects a suitable frequency setting from the frequency settings, forexample, sequentially uses a set of frequency setting and performs thenoise detecting process until the noise interference is within thetolerable range. The frequency switching process may alternativelyinclude selects the best frequency setting from the frequency settings,for example, sequentially uses a set of frequency setting and performsthe noise detecting process, and selects the frequency setting with theleast noise interference, for example, the frequency setting with thesmallest maximum value of the 1D sensing information of noise detection,or the frequency setting with the smallest sum or average of all thevalues of the 1D sensing information of noise detection.

The frequency settings include, but are not limited to, a driving mode,a frequency and a set of parameters. The set of parameters may include,but is not limited to, said resistor parameter, said gain parameter,said phase parameter and said PWM parameter. It can be appreciated byone with ordinary skill in the art that there are other parameterssuitable for the capacitive touch screen and its control circuit.

The frequency settings may include a plurality of driving potentials,such as a first driving potential and a second driving potential, asshown in Table 1 below. It can be appreciated by one with ordinary skillin the art that there can be three or more driving potentials. Eachdriving potential can be divided into several driving modes, including,but not limited to, single-electrode driving mode, two-electrode drivingmode, three-electrode driving mode, four-electrode driving mode etc.Each driving mode of each driving potential includes a plurality offrequencies, each frequency corresponds to a set of parameters justmentioned. It can be appreciated by one with ordinary skill in the artthat the frequencies of each driving mode corresponding to each drivingpotential may be entirely different, or partially the same; the presentinvention is not limited as such.

TABLE 1 Driving Potential Driving Mode Frequency Parameter Set FirstSingle-electrode First frequency First parameter set driving drivingmode First frequency First parameter set potential . . . i^(th)frequency i^(th) parameter set Two-electrode i + 1^(th) frequency i +1^(th) parameter set driving mode i + 2^(th) frequency i + 2^(th)parameter set . . . j^(th) frequency j^(th) parameter set SecondSingle-electrode j + i^(th) frequency j + 1^(th) parameter set drivingdriving mode j + 2^(th) frequency j + 2^(th) parameter set potential . .. k^(th) frequency k^(th) parameter set Two-electrode k + 1^(th)frequency k + 1^(th) parameter set driving mode k + 2^(th) frequency k +2^(th) parameter set . . . n^(th) frequency n^(th) parameter set

According to the above, the present invention proposes a detectingmethod for the capacitive touch screen. Referring to FIG. 3A, first, instep 310, a plurality of frequency settings are stored based on thelevels of power consumption. Each frequency setting corresponds to adriving mode of a driving potential, and each frequency setting has afrequency and a set of parameters, wherein there are at least one typeof driving potential. Next, in step 320, the setting of the detectingcircuit is initialized based on the set of parameter of one of thefrequency settings, and in step 330, signals of the detecting electrodesare detected by the detecting circuit based on a set of parameters ofthe detecting circuit, and 1D sensing information is generated from thesignals of the detecting electrodes. Then, in step 340, it is determinedwhether noise interference exceeds a tolerable range based on the 1Dsensing information. Thereafter, in step 350, when the noiseinterference exceeds the tolerable range, the working frequency and thesetting of the detecting circuit are changed according to the frequencyand the set of parameter of one of the frequency settings, and 1Dsensing information is generated, and then it is again determinedwhether the noise interference exceeds the tolerable range based on the1D sensing information. This step is repeated until the noiseinterference is within the tolerable range. Alternatively, in step 360of FIG. 3B, when the noise interference exceeds the tolerable range, theworking frequency and the setting of the detecting circuit are changedaccording to the frequency and the set of parameter of every of thefrequency settings, and 1D sensing information is generated and then thenoise interference is determined based on the 1D sensing information,and the working frequency and the setting of the detecting circuit arechanged to the frequency and the set of parameter of the frequencysetting that is least interfered by noise.

For example, a detecting device for detecting a capacitive touch sensoris proposed according to a best mode of the present invention, whichincludes a storage circuit 43, a driving circuit 41 and a detectingcircuit 42. As described in step 310, the storage circuit 43 includes aplurality of frequency settings 44 stored according to the levels ofpower consumption. The storage circuit 43 can be a circuit, a memory ora storage media capable of storing electromagnetic records. In anexample of the present invention, the frequency settings 44 can beimplemented as a lookup table. In addition, the frequency settings 44can also store a power consumption parameter.

The driving circuit 41 can be an integration of several circuits,including, but not limited to, the clock circuit 11, the PWM circuit 12,the driving switch 131, the detecting switch 132 and the drivingselecting circuit 141. The circuits listed in this example is merely forillustration purpose, and the driving circuit 41 may only include someof the circuits or add more circuits; the present invention is notlimited as such. The driving circuit is used to provide a driving signalto at least one driving electrode 151 of a capacitive touch screenaccording to a working frequency, wherein the capacitive touch screenincludes a plurality of driving electrodes 151 and a plurality ofdetecting electrodes 152

The detecting circuit 42 can be an integration of several circuits,including, but not limited to, the measuring circuit 18, the amplifyingcircuit 17, the detecting selecting circuit 142, and even the variableresistor 16. The circuits listed in this example is merely forillustration purpose, and the detecting circuit 42 may only include someof the circuits or add more circuits; the present invention is notlimited as such. Furthermore, the detecting circuit 42 may furtherinclude performing the steps 320 to 340, and step 350 or step 360. Inthe example of FIG. 3B, the frequency settings are not necessarilystored according to the levels of power consumption.

As previously described, the 1D sensing information for determiningwhether the noise interference exceeds the tolerable range is generatedwhen no driving signal is provided to the driving electrode(s), forexample, when the driving switch 131 is turned off and the detectingswitch 132 is turned on.

In an example of the present invention, the at least one drivingpotential has several types of driving modes, including asingle-electrode driving mode and a two-electrode driving mode. In thesingle-electrode driving mode, the driving signal is provided to only asingle driving electrode at any instance, while in the two-electrodedriving mode, the driving signal is provided to a pair of drivingelectrodes simultaneously. The level of power consumption of thesingle-electrode driving mode is less than the level of powerconsumption in the two-electrode driving mode. In addition, in thesingle-electrode driving mode, when every driving electrode is driven bythe driving signal, 1D sensing information is generated by the detectingcircuit to constitute a full image. In the two-electrode driving mode,when every pair of driving electrodes is driven by the driving signal,1D sensing information is generated by the detecting circuit toconstitute a reduced image. The number of pixels of the reduced image isless than that of the pixels of the full image. Moreover, in thetwo-electrode driving mode, the detecting circuit may further performsingle-electrode driving on electrodes at either end. When theelectrodes at either end are driven, signals of all the detectingelectrodes are detected to generate 1D sensing information, wherein the1D sensing information for the electrodes at either side are placedoutside the two sides of the reduced image to form the expanded image,and the number of pixels of the expanded image is greater than that ofthe pixels of the full image.

In another example of the present invention, the driving potentialincludes a first driving potential and a second driving potential,wherein the level of power consumption for generating the full image inthe single-electrode driving mode of the first driving potential> thelevel of power consumption for generating the reduced image in thetwo-electrode driving mode of the first driving potential> the level ofpower consumption for generating the full image in the single-electrodedriving mode of the second driving potential.

In yet another example of the present invention, the driving potentialincludes a first driving potential and a second driving potential,wherein the level of power consumption for generating the full image inthe single-electrode driving mode of the first driving potential> thelevel of power consumption for generating the full image in thesingle-electrode driving mode of the second driving potential.

Moreover, in an example of the present invention, the signal of eachdetecting electrode is passed through a variable resistor beforeproviding to the detecting circuit. The detecting circuit sets theimpedance of the variable resistor according to the set of parameter ofone of the frequency settings. In addition, the signals of the detectingelectrodes are first amplified by at least one amplifier before beingdetected. The detecting circuit sets the gain of the amplifier accordingto the set of parameter of one of the frequency settings. In addition,the driving signal is generated according to the set of parameter of oneof the frequency settings.

In an example of the present invention, each value of 1D sensinginformation is generated according to the signals of the detectingelectrodes in a defined period, wherein the defined period is determinedaccording to the set of parameter of one of the frequency settings. Inan example of the present invention, each value of 1D sensinginformation is generated according to the signals of the detectingelectrodes with at least one defined phase, wherein the defined phase isdetermined according to the set of parameter of one of the frequencysettings.

Referring to FIG. 5, a schematic diagram illustrating thesingle-electrode driving mode proposed by the present invention isshown. A driving signal S is sequentially provided to a first drivingelectrode, a second driving electrode . . . and the last drivingelectrode. 1D sensing information for single-electrode driving 52 isgenerated when each driving electrode is driven by the driving signal S.All the 1D sensing information for single-electrode driving 52 arecombined together to constitute a full image 51. Each value of the fullimage 51 corresponds to changes in capacitive coupling of one of theelectrode intersections.

Furthermore, each value of the full image 51 corresponds to a locationof one of the intersections. For example, the center location of eachdriving electrode corresponds to a first 1D coordinate, while the centerlocation of each detecting electrode corresponds to a second 1Dcoordinate. The first 1D coordinate can be one of a lateral (e.g.horizontal or X-axis) coordinate and longitudinal (e.g. vertical orY-axis) coordinate, while the second 1D coordinate can be the other oneof a lateral (e.g. horizontal or X-axis) coordinate and longitudinal(e.g. vertical or Y-axis) coordinate. Each intersection corresponds to a2D coordinate of a driving electrode and a detecting electrodeintersecting thereat. The 2D coordinate is made up of the first 1Dcoordinate and the second 1D coordinate, for example, (first 1Dcoordinate, second 1D coordinate) or (second 1D coordinate, first 1Dcoordinate). In other words, the 1D sensing information generated byeach single-electrode driving corresponds to the first 1D coordinate atthe center of a driving electrode, wherein each value of the 1D sensinginformation for single-electrode driving (or each value of the fullimage) corresponds to a 2D coordinate made up of the first 1D coordinateat the center of the driving electrode and the second 1D coordinate atthe center of a detecting electrode. Similarly, each value of the fullimage corresponds to the center location of one of the intersections,that is, corresponds to a 2D coordinate made up of the first 1Dcoordinate at the center of a driving electrode and the second 1Dcoordinate at the center of a detecting electrode.

Referring to FIG. 6, a schematic diagram illustrating the two-electrodedriving mode proposed by the present invention is shown. A drivingsignal S is sequentially provided to a first pair of driving electrodes,a second pair of driving electrodes . . . and the last pair of drivingelectrodes. 1D sensing information for two-electrode driving 62 isgenerated when each pair of driving electrodes is driven by the drivingsignal S. In other words, N driving electrodes make up N−1 (multiple)pairs of driving electrodes. All the 1D sensing information fortwo-electrode driving 62 are combined together to constitute a reducedimage 61. The number of values (or pixels) of the reduced image 61 isless than the number of values (or pixels) of the full image 51. Incontrast to the full image, each 1D sensing information fortwo-electrode driving 62 of the reduced image corresponds to a first 1Dcoordinate of a center location between a pair of driving electrodes,and each value corresponds to a 2D coordinate made up of the first 1Dcoordinate of the center location between the pair of driving electrodesand a second 1D coordinate at the center of a detecting electrode. Inother words, each value of the reduced image corresponds to the locationof the center between a pair of intersections, that is, corresponds to a2D coordinate made up of the first 1D coordinate of the center locationbetween a pair of driving electrodes (or one of several pairs of drivingelectrodes) and a second 1D coordinate at the center of a detectingelectrode.

Referring to FIG. 7A, a schematic diagram illustrating a first sidesingle-electrode driving in the two-electrode driving mode proposed bythe present invention is shown. A driving signal S is provided to adriving electrode nearest to a first side of a capacitive touch screen,and first-side 1D sensing information for single-electrode driving 721is generated when the driving electrode nearest to the first side of thecapacitive touch screen is being driven by the driving signal S. Nowreferring to FIG. 7B, a schematic diagram illustrating a second sidesingle-electrode driving in the two-electrode driving mode proposed bythe present invention is shown. A driving signal S is provided to adriving electrode nearest to a second side of a capacitive touch screen,and second-side 1D sensing information for single-electrode driving 722is generated when the driving electrode nearest to the second side ofthe capacitive touch screen is being driven by the driving signal S. The1D sensing information for single-electrode driving 721 and 722generated when the driving electrodes nearest to the first and secondsides of the capacitive touch screen are being driven are placed outsidethe first and second sides of the reduced image 61 mentioned before,respectively, to form an expanded image 71. The number of values (orpixels) in the expanded image 71 is greater than the number of values(or pixels) in the full image 51. In an example of the presentinvention, the first-side 1D sensing information for single-electrodedriving 721 is generated first, then the reduced image 61 is generated,and then the second-side 1D sensing information for single-electrodedriving 722 is generated to construct the expanded image 71. In anotherexample of the present invention, the reduced image 61 is generatedfirst, and thereafter, the first- and second-side 1D sensing informationfor single-electrode driving 721 and 722 are generated to construct theexpanded image 71.

In other words, the expanded image is made up of the first-side 1Dsensing information for single-electrode driving, the reduced image andthe second-side 1D sensing information for single-electrode driving.Since the values in the reduced image 61 are two-electrode driven, sothe average magnitude will be greater than that of the first- andsecond-side 1D sensing information for single-electrode driving. In anexample of the present invention, the values of the first- andsecond-side 1D sensing information for single-electrode driving 721 and722 are first amplified by a ratio before placing outside the first andsecond sides of the reduced image 61. This ratio can be a predeterminedmultiple greater than 1, or based on the ratio between the values of the1D sensing information for two-electrode driving and the values of the1D sensing information for single-electrode driving, for example, theratio between the sum (or average) of all the values of the first-side1D sensing information for single-electrode driving 721 and the sum (oraverage) of all the values of the 1D sensing information 62 near thefirst side in the reduced image, and the values of the first-side 1Dsensing information for single-electrode driving 721 are amplified bythis ratio before placing outside the first side of the reduced image61. Similarly, the values of the second-side 1D sensing information forsingle-electrode driving 722 are amplified by this ratio before placingoutside the second side of the reduced image 61. Alternatively, forexample, said ratio is the ratio between the sum (or average) of all thevalues in the reduced image 61 and the sum (or average) of all thevalues of the first- and second-side 1D sensing information forsingle-electrode driving 721 and 722.

In the single-electrode driving mode, each value (or pixel) of the fullimage corresponds to a 2D location (or coordinate) of an intersectionmade up of the first 1D location (or coordinate) corresponding to thedriving electrode and the second 1D location (or coordinate)corresponding to the detecting electrode intersecting at theintersection, for example (first 1D location, second 1D location) or(second 1D location, first 1D location). A single external conductiveobject may be capacitively coupled to one or more intersections. Theintersection(s) capacitively coupled to the external conductive objectgenerate(s) changes in capacitive coupling, which are reflected in thecorresponding value(s) in the full image, that is, in the correspondingvalue(s) in the full image corresponding to the external conductiveobject. Thus, based on the corresponding values and 2D coordinates inthe full image corresponding to the external conductive object, acentroid location (a 2D coordinate) of the external conductive objectcan be calculated.

In an example of the present invention, in the single-electrode drivingmode, the 1D location corresponding to each electrode (driving anddetecting electrodes) is the location of the center of the electrode.Based on another example of the present invention, in the two-electrodedriving mode, the 1D location corresponding to each pair of electrodes(driving and detecting electrodes) is the location of the center betweenthe two electrodes.

In the reduced image, a first 1D sensing information corresponds to thecenter location of a first pair of driving electrodes, that is, a first1D location of the center between a first and a second drivingelectrodes (the first pair of driving electrodes). If the centroidlocation is simply calculated, a location can be calculated only in therange from the center of the first pair of driving electrodes to thecenter of the last pair of driving electrodes. The range in which thelocation is calculated based on the reduced image lacks a range from thecenter location of the first driving electrode to the center location(the first 1D location of the center) of the first pair of drivingelectrodes, and a range from the center location of the last pair ofdriving electrodes to the center location of the last driving electrode.

In contrast to the reduced image, in the expanded image, the first- andsecond-side 1D sensing information correspond to the center locations ofthe first and last driving electrodes, respectively. Thus, the range inwhich the location is calculated based on the expanded image, comparedto that calculated based on the reduced image, further includes therange from the center location of the first driving electrode to thecenter location (the first 1D location of the center) of the first pairof driving electrodes, and the range from the center location of thelast pair of driving electrodes to the center location of the lastdriving electrode. In other words, the range in which the location iscalculated based on the expanded image covers the range in which thelocation is calculated based on the full image.

Similarly, the two-electrode driving mode can be further expanded to amultiple-electrode driving mode, that is, multiple driving electrodesare simultaneously driven. In other words, the driving signal issimultaneously provided to multiple (or all) driving electrodes in a setof driving electrodes. The number of driving electrodes in a set ofdriving electrodes may, for example, be two, three or four. Themultiple-electrode driving mode includes the two-electrode driving mode,but not the single-electrode driving mode.

Referring to FIG. 8, a detecting method for a capacitive touch screenproposed by the present invention is shown. In step 810, a capacitivetouch screen including a plurality of parallel driving electrodes and aplurality of parallel detecting electrodes is provided, wherein thedriving electrodes and the detecting electrodes (e.g. the drivingelectrodes 151 and the detecting electrodes 152) cross each other atintersections. Next, in step 820, one and a set of driving electrodesamong the plurality of driving electrodes is/are provided with a drivingsignal in the single-electrode driving mode and the multiple-electrodedriving mode, respectively, that is, one of the driving electrodes aredriven by the driving signal at a time in the single-electrode drivingmode, while a set of driving electrodes in the driving electrodes aresimultaneously driven by the driving signal at a time in themultiple-electrode driving mode, wherein apart from the last N drivingelectrodes, each driving electrodes and two successive drivingelectrodes form the set of driving electrodes to be drivensimultaneously, and N is the number of the set minus one. The drivingsignal can be provided by the driving circuit 41 described before.Thereafter, in step 830, each time the driving signal is provided, 1Dsensing information is obtained via the detecting electrodes; morespecifically, a plurality of 1D sensing information formultiple-electrode driving are obtained in the multiple-electrodedriving mode and first- and second-side 1D sensing information forsingle-electrode driving are obtained in the single-electrode drivingmode. For example, in the multiple-electrode driving mode, one 1Dsensing information for multiple-electrode driving is obtained when eachset of driving electrodes are provided with the driving signal.Alternatively, for example, in the single-electrode driving mode, onefirst-side 1D sensing information for single-electrode driving and onesecond-side 1D sensing information for single-electrode driving areobtained when the first driving electrode and the last driving electrodeare provided with the driving signal, respectively. The 1D sensinginformation can be obtained by the detecting circuit 42 described above.The 1D sensing information thus includes the 1D sensing information formultiple-electrode driving (reduced image) and the first- andsecond-side 1D sensing information for single-electrode driving. Then,in step 840, an image (an expanded image) is generated according to thefirst-side 1D sensing information for single-electrode driving, all the1D sensing information for multiple-electrode driving and thesecond-side 1D sensing information for single-electrode driving. Step840 can be performed by the control circuit described before.

As described before, the potential of the driving signal in thesingle-electrode driving mode is not necessary the same as the potentialof the driving signal in the multiple-electrode driving mode; they canbe the same or different. For example, the single-electrode driving isperformed with a first AC potential larger than a second AC potentialfor the multiple-electrode driving. The ratio of the first AC potentialto the second AC potential can be a predetermined ratio. In addition, instep 840, the image is generated based on all the values of the first-and second-side 1D sensing information for single-electrode drivingbeing multiplied by the same predetermined ratio or differentpredetermined ratios. Moreover, the frequency of the driving signal inthe single-electrode driving mode can be different from that of thedriving signal in the multiple-electrode driving mode.

The number of driving electrodes in the set of driving electrodes can betwo, three or more; the present invention is not limited to these. In apreferred mode of the present invention, the number of drivingelectrodes in the set of driving electrodes is two. When the number ofdriving electrodes in the set of driving electrodes is two, each drivingelectrode corresponds to a first 1D coordinate, wherein 1D sensinginformation driven by each group (or pair) of the electrodes correspondsto a first 1D coordinate of the center between the pair of drivingelectrodes among the plurality of driving electrodes, and the first- andsecond-side 1D sensing information for single-electrode drivingcorrespond to first 1D coordinates of the first and the last drivingelectrodes, respectively.

Similarly, when the number of driving electrodes in the set of drivingelectrodes is more than two, each driving electrode corresponds to afirst 1D coordinate, wherein 1D sensing information driven by each setof multiple electrodes corresponds to a first 1D coordinate of thecenter between two driving electrode separated the furthest in the setof driving electrodes, and the first- and second-side 1D sensinginformation for single-electrode driving correspond to first 1Dcoordinates of the first and the last driving electrodes, respectively.

Moreover, each detecting electrode corresponds to a second 1Dcoordinate, and each value of each 1D sensing information corresponds tothe second 1D coordinate of one of the detecting electrodes.

The above embodiments are only used to illustrate the principles of thepresent invention, and they should not be construed as to limit thepresent invention in any way. The above embodiments can be modified bythose with ordinary skill in the art without departing from the scope ofthe present invention as defined in the following appended claims.

What is claimed is:
 1. A detecting device for a capacitive touch screen,comprising: a capacitive touch screen including a plurality of drivingelectrodes and a plurality of detecting electrodes, wherein the drivingelectrodes and the detecting electrodes cross each other at a pluralityof intersections; a driving circuit for providing a driving signal,wherein in a single-electrode driving mode, the driving signal isprovided to only one of the driving electrodes at a time, while in amultiple-electrode driving mode, the driving signal is simultaneouslyprovided to a set of driving electrodes at a time, wherein apart fromthe last N driving electrodes, each driving electrode and two successivedriving electrode construct the set of driving electrodes beingsimultaneously driven, and N is the number of the set of drivingelectrode minus one; and a detecting circuit, each time the drivingsignal being provided, obtaining one-dimensional (1D) sensinginformation from the detecting electrodes, wherein in themultiple-electrode driving mode, a 1D sensing information formultiple-electrode driving is obtained when each set of drivingelectrodes are provided with the driving signal, and in thesingle-electrode driving mode, a first-side 1D sensing information forsingle-electrode driving and a second-side 1D sensing information forsingle-electrode driving are obtained when the first driving electrodeand the last driving electrode are provided with the driving signal,respectively; and a control circuit for generating an image based on thefirst-side 1D sensing information for single-electrode driving, all the1D sensing information for multiple-electrode driving and thesecond-side 1D sensing information for single-electrode driving.
 2. Thedetecting device of claim 1, wherein the potential of the driving signalin the single-electrode driving mode is different from that of thedriving signal in the multiple-electrode driving mode.
 3. The detectingdevice of claim 1, wherein the frequency of the driving signal in thesingle-electrode driving mode is different from that of the drivingsignal in the multiple-electrode driving mode.
 4. The detecting deviceof claim 1, wherein the image is generated based on all values of thefirst- and second-side 1D sensing information for single-electrodedriving being multiplied by the same predetermined ratio.
 5. Thedetecting device of claim 1, wherein the image is generated based on allvalues of the first- and second-side 1D sensing information forsingle-electrode driving being multiplied by different predeterminedratios.
 6. The detecting device of claim 1, wherein the number ofdriving electrodes in the set of driving electrode being simultaneouslydriven is two.
 7. The detecting device of claim 1, wherein each drivingelectrode corresponds to a first 1D coordinate, wherein eachmultiple-electrode driven 1D sensing information corresponds to a first1D coordinate of the center between a pair of driving electrodes amongthe plurality of driving electrodes, and the first- and second-side 1Dsensing information for single-electrode driving correspond to first 1Dcoordinates of the first and the last driving electrodes, respectively.8. The detecting device of claim 1, wherein the number of drivingelectrodes in the set of driving electrode being simultaneously drivenis three.
 9. The detecting device of claim 1, wherein each drivingelectrode corresponds to a first 1D coordinate, wherein eachmultiple-electrode driven 1D sensing information corresponds to a first1D coordinate of the center between two driving electrodes that arefurthest apart in a set of driving electrodes among the plurality ofdriving electrodes, and the first- and second-side 1D sensinginformation for single-electrode driving correspond to first 1Dcoordinates of the first and the last driving electrodes, respectively.10. The detecting device of claim 1, wherein each 1D sensing informationcorresponds to a first 1D coordinate, and each detecting electrodecorresponds to a second 1D coordinate, and each value of each 1D sensinginformation corresponds to the second 1D coordinate of one of thedetecting electrodes.
 11. A detecting method for a capacitive touchscreen, comprising: providing a capacitive touch screen including aplurality of driving electrodes and a plurality of detecting electrodes,wherein the driving electrodes and the detecting electrodes cross eachother at a plurality of intersections; providing a driving signal,wherein in a single-electrode driving mode, the driving signal isprovided to only one of the driving electrodes at a time, while in amultiple-electrode driving mode, the driving signal is simultaneouslyprovided to a set of driving electrodes at a time, wherein apart fromthe last N driving electrodes, each driving electrode and two successivedriving electrode construct the set of driving electrodes beingsimultaneously driven, and N is the number of the set of drivingelectrode minus one; and each time the driving signal being provided,obtaining one-dimensional (1D) sensing information from the detectingelectrodes, wherein in the multiple-electrode driving mode, a 1D sensinginformation for multiple-electrode driving is obtained when each set ofdriving electrodes are provided with the driving signal, and in thesingle-electrode driving mode, a first-side 1D sensing information forsingle-electrode driving and a second-side 1D sensing information forsingle-electrode driving are obtained when the first driving electrodeand the last driving electrode are provided with the driving signal,respectively; and generating an image based on the first-side 1D sensinginformation for single-electrode driving, all the 1D sensing informationfor multiple-electrode driving and the second-side 1D sensinginformation for single-electrode driving.
 12. The detecting method ofclaim 11, wherein the potential of the driving signal in thesingle-electrode driving mode is different from that of the drivingsignal in the multiple-electrode driving mode.
 13. The detecting methodof claim 11, wherein the frequency of the driving signal in thesingle-electrode driving mode is different from that of the drivingsignal in the multiple-electrode driving mode.
 14. The detecting methodof claim 11, wherein the image is generated based on all values of thefirst- and second-side 1D sensing information for single-electrodedriving being multiplied by the same predetermined ratio.
 15. Thedetecting method of claim 11, wherein the image is generated based onall values of the first- and second-side 1D sensing information forsingle-electrode driving being multiplied by different predeterminedratios.
 16. The detecting method of claim 11, wherein the number ofdriving electrodes in the set of driving electrode being simultaneouslydriven is two.
 17. The detecting method of claim 11, wherein eachdriving electrode corresponds to a first 1D coordinate, wherein eachmultiple-electrode driven 1D sensing information corresponds to a first1D coordinate of the center between a pair of driving electrodes amongthe plurality of driving electrodes, and the first- and second-side 1Dsensing information for single-electrode driving correspond to first 1Dcoordinates of the first and the last driving electrodes, respectively.18. The detecting method of claim 11, wherein the number of drivingelectrodes in the set of driving electrode being simultaneously drivenis three.
 19. The detecting method of claim 11, wherein each drivingelectrode corresponds to a first 1D coordinate, wherein eachmultiple-electrode driven 1D sensing information corresponds to a first1D coordinate of the center between two driving electrodes that arefurthest apart in a set of driving electrodes among the plurality ofdriving electrodes, and the first- and second-side 1D sensinginformation for single-electrode driving correspond to first 1Dcoordinates of the first and the last driving electrodes, respectively.20. The detecting method of claim 11, wherein each 1D sensinginformation corresponds to a first 1D coordinate, and each detectingelectrode corresponds to a second 1D coordinate, and each value of each1D sensing information corresponds to the second 1D coordinate of one ofthe detecting electrodes.